Concavibalcis Warén, 1980

Takano, Tsuyoshi, Tsuzuki, Shouji & Kano, Yasunori, 2022, Description of a second species of the eulimid genus Concavibalcis (Gastropoda: Vanikoroidea), Zootaxa 5093 (3), pp. 397-400 : 397

Genus Concavibalcis Warén, 1980

Type species. Concavibalcis scalaris Warén, 1980 , by original designation.

Remarks. The holotype of C. scalaris (Smithsonian National Museum of Natural History, USNM 277426) was collected from 390 m off Motocot Point, Luzon Island, the Philippines ( Warén 1980b: 294). Its shell is characterized by (1) a height of 5.1 mm, (2) a conical outline, (3) a slightly chalky appearance, (4) a blunt apex without clear demarcation between the protoconch and teleoconch, (5) shouldered, distinctly concave teleoconch whorls, (6) an ovate aperture, and (7) a strongly curved outer lip ( Warén 1980b: figs. 32–34, 1983a).

Warén (1980b) noted some resemblance between C. scalaris and certain species of Zebina H. Adams & A. Adams, 1854 ( Caenogastropoda: Rissooidea: Zebinidae ) in teleoconch morphology. The latter genus is, however, characterized by an aperture with a more developed basal notch and a straight, opisthocline outer lip ( Warén 1980b; Ponder 1985). Concavibalcis scalaris is also similar to Turriodostomia nakayamai ( Habe, 1961) (Heterobranchia: Pyramidelloidea: Pyramidellidae ) in sharing shouldered, concave teleoconch whorls, whereas only the latter species has a strong columellar fold in the aperture ( Habe 1961). The familial assignment of C. scalaris to Eulimidae is justified by the simple shell aperture without a basal notch or a columellar fold and by a probable lack of a radula ( Warén 1980b). The presence of incremental scars in the present new species (see below) further corroborates the eulimid affinity of Concavibalcis .